The present invention generally relates to lighting devices and, more particularly, to a portable lighting device, such as a headlamp that can be worn on the head of a user.
Portable lighting devices, such as flashlights and headlamps, generally employ a light source, such as an incandescent lamp or one or more light emitting diodes (LEDs), a reflector, a lens, and a power source, such as one or more electrochemical cell batteries. A conventional headlamp typically includes a strap adapted to fit on the head of a user to position the headlamp in the vicinity of a user's forehead. Most conventional headlamps provide a fixed light beam or allow for a selection of various combinations of LEDs to provide different color and intensities of light illumination. Some flashlights allow movement of the reflector to change the light beam, which often results in a non-uniform beam intensity.
Lighting devices, such as headlamps, employ light sources that generate thermal energy (heat). To enhance performance with a light source such as an LED, the LED is generally required to operate below extreme temperatures. When the LED operates at an elevated temperature, the output light intensity, typically measured in lumens, and output light efficiency usually decreases. Thus, there is a need to prevent overheating of the LED to provide efficient lighting performance. Additionally, in conventional headlamp assemblies, heat generated by the light source usually is conducted towards the rear of the headlamp and may be transferred to the user's forehead, which may be undesirable.
Accordingly, it is therefore desirable to provide for a portable lighting device, such as a headlamp, that effectively controls the temperature and maintains a desired operating temperature of the light source and provides a desirable light illumination beam.